VU#862559: crypton-x509-validation Haskell libraries do not enforce X.509 NameConstraints

Summary

Overview A vulnerability has been discovered in the Haskell TLS software stack, commonly used by applications built in the Haskell programming language to securely connect to servers over the internet. Specifically, the libraries "crypton-x509-validation" fail to enforce a key security feature called NameConstraints, a standard defined in RFC 5280 that helps organizations control which domains a certificate authority (CA) is allowed to issue certificates for. This vulnerability allows an attacker with access to the sub-CA to create certificates that will validate successfully with any Haskell TLS connection, allowing the attacker access to full session visibility. Version 1.91 for crypton-x509-validation have been released to address the vulnerability, tracked as CVE-2026-9648. Description Haskell is a programming language often used in... Related CVEs: CVE-2026-9648.

Why it matters

CERT/CC notes often cover coordinated disclosures, multi-vendor exposure, infrastructure risk, or cases where remediation guidance is still developing.

Operator check

Review the CERT/CC Vulnerability Note and compare the affected vendor and product list against your inventory. Apply vendor fixes or compensating controls for crypton-x509-validation Haskell libraries do not enforce X.509 NameConstraints where available.

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